1. Field of the Invention
This invention is an electronic apparatus for control of closed-loop systems.
2. Description of Prior Art
Closed-loop control is common to many electronic applications. Examples include: voltage control of a switching power supply, velocity control of an industrial motor, temperature control of a household appliance, or current control of a linear amplifier in automatic test equipment. Closed-loop control is accomplished by adjusting an output driver until an input sensor or feedback signal matches a desired setpoint. Improper design can result in large errors, slow response, or instability.
Traditional closed-loop controllers have been comprised of either analog circuitry or software driven microprocessors. Analog circuitry requires a large number of components, specialized design expertise, and must be physically altered to modify performance or functionality. Microprocessors allow software to be modified without physically altering the circuit, but still require long programming cycles by specialized personnel and are subject to the performance limitations of standard processors. In both cases, development efforts are long and expensive.
Specialized motion control integrated circuits have been developed, such as the LM628 by National Semiconductor or the HCTL-1100 by Hewlett. Packard. These devices decrease development time by incorporating common motion control components and features that may selected through a host processor. However, these devices lack flexibility since there are designed for specific applications containing brush DC motors with digital encoder feedback. For example, they could not be used to regulate voltage in a power supply, temperature in an appliance, or current in a linear amplifier. Another limitation is that they are not autonomous since they require a host processor.
U.S. Pat. No. 6,031,749 discloses a power module that is intended to be universal but only satisfies a limited subset of closed-loop applications, namely lighting applications. The control laws and architecture disclosed are specific to lighting applications and are not universal.
U.S. Pat. No. 6,005,377 discloses a programmable controller for switching power conversion that does not utilize software or analog circuitry. This patent describes a Field Programmable Gate Array (FPGA) that utilizes lookup tables based on analog inputs. This controller requires extensive development time by personnel with specialized expertise and equipment. It may not be quickly and easily modified since the patent specifically excludes software dependence.
U.S. Pat. No. 5,371,670 discloses a controller with a tilt term in the compensation network. This compensation network has adjustable gains but no means are disclosed to reconfigure the controller to applications other than invariant linear systems. A fixed signal path is shown with no selectable options other than adjustable compensator gains.
U.S. Pat. No. 4,788,647 discloses a controller for hydroelectric power plants. Limited configuration of application specific components within an application specific architecture allows adaptation to a particular hydroelectric power plant. The specialized components and architecture with limited configuration capability preclude adaptation to applications other than hydroelectric power generation.
These products and patents indicate the strong need for a flexible closed-loop controller that is capable of satisfying a broad range of applications with minimal development time and expertise.
This invention is a flexible closed-loop controller that may be quickly and easily configured for a broad range of applications.
This invention takes advantage of the fact that virtually all closed-loop control applications contain the same basic elements, whose configuration is application dependent. By incorporating configurable control elements with automated configuration management, a flexible closed-loop controller is achieved that may be quickly and easily configured for a broad range of applications. Accordingly, several objects and advantages of this invention are:
a) reduced development time since the user only needs to select configuration settings for the controller, rather than design the controller architecture;
b) reduced development cost since extensive expertise or specialized equipment is not required to configure the controller, as built-in configuration management automates the process;
c) reduced parts count since a single controller contains all the elements required for closed-loop control;
d) reduced parts cost since the flexible closed loop controller can be manufactured in mass volume for a large number of markets and applications;
e) improved performance since the invention is developed specifically for closed-loop applications;
f) improved reliability since the same controller is tested in a variety of applications by a variety of users.
Further objects and advantages of this invention will become apparent from a consideration of the drawings and ensuing description.